I have 300K on my Dodge Cummins 12 valve - and it is still runs like new one. Pulled the 10K lb boat to Mexico and back (3K miles) and it did not use or leak a drop of oil (yes, even I was surprised) and we were pulling some horrendous passes too. But, I know several guy with 750K to one million miles on their B 5.9 who are still going strong. In fact Cummins is now issuing grill badges for the very high mile Dodges - one friend's truck looks like a well decorated war hero. Diesels are good.